Carboxy vinyl polymer and partially hydrolyzed polyacrylamide mobility control agent and process

ABSTRACT

Aqueous solutions containing 10-10,000 ppm of a carboxy vinyl polymer (e.g., Carbopol 961) and 10-10,000 ppm of a partially hydrolyzed polyacrylamide (e.g., Dow 700) impart improved oil recovery in flooding subterranean oil-bearing formations.

United States Patent 1 Norton et al.

(111 3,891,567 June 24, 1975 CARBOXY VINYL POLYMER AND PARTIALLY l-IYDROLYZED POLYACRYLAMIDE MOBILITY CONTROL AGENT AND PROCESS Inventors: Charles J. Norton; David 0. Folk, both of Denver, Colo.

Assignee: Marathon Oil Company, Findlay,

Ohio

Filed: Oct. 23, 1973 Appl. No.: 408,711

Related U.S. Application Data Division of Ser. No. 238,143, March 27, 1972, Pat. No. 3,825,069.

U.S. C1. 252/8-55 D; 166/275 Int. Cl E2lb 43/22; E21b 43/16 Field of Search 25218.55 D; 166/275 [56] References Cited UNITED STATES PATENTS 3,743,018 7/1973 Norton et a1. 252/865 D 3,747,676 7/l973 Norton et a1. 252/8.55 D

3,780,806 12/1973 Bott 252/855 Primary Examiner-Leland A. Sebastian Attorney, Agent, or Firm-J. C. Herring; Richard C.

Willson, .Ir.; J. L. Hummel 57] ABSTRACT 10 Claims, 2 Drawing Figures PATENTEUJUN 24 I975 I I00 I00 0 CARBOXY VINYL POLYACRYLAMIOE 0.65 zummum CONCENTRATION PPM 0 POLYACRYLAMIDE 50 I00 CARBOXY VINYL 5O Fljg. 2

PERCENT THICKENER CARBOXY VINYL POLYMER AND PARTIALLY HYDROLYZED POLYACRYLAMIDE MOBILITY CONTROL AGENT AND PROCESS CROSS REFERENCES TO RELATED APPLICATIONS This is a divisional of Pat. application identified by U.S. Ser. No. 238,143 filed Mar. 27. 1972, now U.S. Pat. No. 3,825,069.

The following cases relate to the same general field as that of the present invention:

U.S. Pat. No. 3,507,331 issued 4/21/70,

U.S. Pat. No. 3,467,187 issued 9/16/69,

U.S. Pat. No. 3,677,344 issued 8/18/72,

U.S. Pat. No. 3,724,545 issued 4/3/73,

U.S. Pat. No. 3,670,820 issued 6/20/72,

U.S. Pat. No. 3,692,113 issued 9/19/72,

U.S. Pat. No. 3,684,014 issued 8/15/72,

Ser. No. 126,731 filed Mar. 22, 1971,

U.S. Pat. No. 3,746,094 issued 8/17/73,

U.S. Pat. No. 3,886,310 issued 12/4/73,

U.S. Pat No. 3,825,068 issued 7/23/74,

Ser. No. 220,910 filed 1/26/72.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to an aqueous composition containing polymers useful for flooding reservoirs to recover crude oil therefrom.

DESCRIPTION OF THE PRIOR ART Water flooding with mobility-reducing agents, e.g., high molecular weight partially hydrolyzed polyacrylamides, such as Dow Chemical Company 700, has been successfully used to recover increased amounts of oil in secondary recovery methods. U.S. Pat. No. 2,827,964, teaches secondary recovery of petroleum from subterranean formations using water-soluble partially hydrolyzed acrylamide polymer. U.S. Pat. No. 3,724,545 teaches improved mobility control of petroleum recovery by injecting at least two slugs, one containing a per meability reduction agent, e.g., partially hydrolyzed, high molecular weight polyacrylamide, and the other slug containing a fluid viscosity-increasing agent, e.g., a linear polysaccharide or other bipolymer.

Carboxy vinyl polymers (CVP), e.g., B. F. Goodrich Chemical Companys Carbopol, (described in their Service Bulletin GC-36) have been used as viscosityincreasing agents in secondary recovery operations. However, the present invention embodies the discovery that a combination of two agents provides unexpected increase in the efficiency of petroleum recovery, substantially above that which would be expected from an examination of data on the use of either of the polymers alone. The prior art discussed in the aforementioned related applications also has applicability to the general field of the present invention.

A design criterion for an optimum flooding process is to have the mobility of the displacing fluid about equal to or less than that of the combination of the formation fluids (hydrocarbon and interstitial water) within the reservoir. This has usually been accomplished by injecting into the water flood a single agent to effect a reduction in mobility. Most commonly, this agent is a partially hydrolyzed, high molecular weight polyacrylamide.

SUMMARY OF THE INVENTION This invention relates to a method of improving mobility control of a flooding process by injecting an aqueous solution of CVP and partially hydrolyzed polyacrylamide into the oil bearing formation. The result of the injection of this aqueous solution is a substantial increase in the screen factor property and also the production of petroleum from subterranean formations.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows the unexpected synergistic improvement in screen factor obtained with a thickener formulation comprised of 50% CVP and 50% partially hydrolyzed polyacrylamide (Dow 700).

FIG. 2 compares the oil recoveries obtained at various compositions of thickener, all used at 500 ppm concentration and used to push a 0.03 pore volume of surfactant slug. The magnitude of the synergism attained with up to 50% partially hydrolyzed polyacrylamide (Pl-IPA) with CVP is indicated by the area between the two curves.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Starting Materials:

By carboxy vinyl polymer" is meant herein high molecular weight polymers containing predominantly carboxy vinyl monomer units.

By partially hydrolyzed polyacrylamide" is meant herein polyacrylamide which has been hydrolyzed to 0.1 to more preferably to l to 45%, most preferably 5 to 30%, of theory.

Partially hydrolyzed polyacrylamide will preferably have molecular weights in the range above 0.1 X 10, preferably from 0.5 to 40 X 10, more preferably from 1 X 10 to 15 X 10 and most preferably from 3 X 10 to 10 X 10. Preferably the partially hydrolyzed polyacrylamide will be present in amounts of from about 0.001 to about 10.0, more preferably from 0.01 to about 1.0, and most preferably from 0.02 to about 0.2 weight percent based on the weight of the total solution.

The carboxy vinyl polymer (CVP) will preferably have a molecular weight above 0.1 X [0, preferably 0.5 to about 20 X 10, more preferably from 1 to about 15 X 10, and most preferably from 3 X 10 to about 10 x 10.

Preferably, the CVP will be present in amounts from about 0.001 to about 10, more preferably from 0.01 to about L0, and most preferably from 0.02 to about 0.2 weight percent based on the total solution.

The solvent for the liquid solutions of the present invention are comprised of water, most preferably consist essentially of connate water, for example, Palestine line water, fresh water, or brackish water. It is preferable that the water contain less than about 300,000, more preferably less than about 10,000, and most preferably less than about 500 parts per million of dissolved solids. The resulting aqueous solution of CVP and partially hydrolyzed polyacrylamide will preferably have viscosity of from about 1.5,to about 1,000 cps, more preferably from about 5 to about 500 cps, and most preferably from 10 to about cps.

While not necessary to the practice of the present invention, various other ingredients including among others, cellulose derivatives and surfactants, e.g., polyalkyl 3 aryl sulfonate and other conventional displacement fluid additives may be added to the liquid polymer solutions.

Preparation of Liquid Systems: It will generally be by the preliminary data on pore volumes (PV), porosities, permeabilities (md), initial oil and water saturations (0,, W,) residual oil and water saturations (O and W,) after preparation simulated water flood with preferable to merely co-mix CVP and the partially hy- 5 a yp Henry fifild P Watch and Similar efficiendrolyzed polyacrylamide and then add water while (lies of Water ry gently stirring to promote dispersion, suspension, and In all p rim nts floods a 0.03 PV slug of a petrosolution. Bubbling a small amount of non-reactive gas, leum Sulfenate was pushed in he econdary e.g., natural gas, may be used to effect mild stirring. flooding operation by up to about I PV of the particu- The ingredients will ref rabl b mix d t bi t to lar thickened water. In each example the injection of temperature, more preferably from 0C. to b r thickened water was continued to the point at which no l00C., and most preferably from C. to about 50C. additional oil was recovered. The data are summarized If desired, a mixing operation can be employed in one in Table l, the last column of which lists the percent or more full-type mixers or mixing tees so long as the oil recovery based on residual oil remaining after the proportions of the ingredients are properly measured 15 preliminary water flood. and thoroughly mixed. Bacteriocides and antioxidants The synergistic effect of thickened water prepared can be advantageously added to preserve the viscosity fro mixed compositions of partially hydrolyzed polyof the solution. acrylamide and CVP are illustrated on FIG. 2.

Table I SUMMARY OF THICKENED WATER RECOVERIES Penneability md Poro- Ex. fi y.

Run

No. CC I Total Thickened Water Recovery W, Eff. "Dtickener PV of O 4 (J9l37 I092 780.4 62.5

3 in. diameter by 4 R. long Berea sandstone (fired at SZS'F.) was 6L6 39.8 500 rn partially ydro lyzed polyacrlamide 500 p m partially ydrolyzed polyacrlamide 250 in partially ydro lyzed polyacrlamide 250 ppm carboxyvgigl polymer 5 ppm carboxy vinyl polymer first saturated with artificial Henry plant brine (containing 1 1,000 ppm C1. 6500 ppm Na. 276 ppm Ca. [67 ppm Mg) and Henry Crude to an initial oil saturation (0,) and initial water saturation (W t; the core was subsequently flooded to residual saturation (O,

and W,) and then flood at rates of 1.9 to 3.7 lt/day with 0.03 PV of FF-56l slug (petroleum sulfonate slug) followed by up Water (containing 400 ppm NaCl and 55 ppm CaCl,)

Screen Factor: Aqueous solutions of CV? and partially hydrolyzed polyacrylamide are prepared by to Society of Petroleum Engineers Paper No. 2867. and

the test results are summarized in FIG. 1.

EXAMPLES EXAMPLES I-IV Examples I through IV are run under identical conditions.

A 3 inch diameter by 4 foot Berea sandstone cylindrical core is prepared to simulate a condition at the termination of a preliminary secondary water-flood operation. This condition is achieved by first saturating the core with artificial Henry field water, then partially displacing this water with Henry field crude oil until saturated with crude (0,, W and finally water flooding with artificial Henry water to residual oil (0,) and residual water (W,) saturations.

The comparabilities of the examples employing various thickeners in recovery operations are established to I re volume of synthetic Palestine and the additional crude recovered and calculated as percent of residual oil in the care before this final flood.

Modification of the Invention It will be understood by those skilled in the art that the relative proportions of the admixture of CV? and partially hydrolyzed polyacrylamides utilized in the examples herein are merely exemplary of the relative proportions which may be employed with the present invention. For example, using nearly CVP at the leading edge of the displacement slug and gradually using a higher and higher percentage of partially hydrolyzed polyacrylamides, to provide a slug which is rich at its leading edge where depletion is most likely to occurxlnitial viscosity of the slug may be the same at all points throughout the slug or may be itself gradually decreased until it approaches that of the drive fluid which displaces the slug through the formation.

What is claimed is:

1. Compositions comprising aqueous solutions of about 0.001% to about l0% of partially hydrolyzed polyacrylamide and about 0.001% to about 10% of carboxy vinyl polymers, the percents based on total weight of the solution.

2. Compositions according to claim 1 wherein the partially hydrolyzed polyacrylamide had a molecular weight of about 500,000 to about 20,000,000 and is hydrolyzed to about 0.1 to about 70% of theory.

3. Compositions according to claim 1 wherein the partially hydrolyzed polymer is present in a concentration of about 0.01 to about 1.0%.

4. A composition according to claim 1 wherein the aqueous solution is characterized by a viscosity of about 1.5 to about 1,000 centipoises.

5. A composition according to claim 1 wherein the aqueous solution is characterized by a viscosity of about 5 to about 500 centipoises.

6. A composition according to claim 1 wherein the aqueous solution is characterized by a viscosity of UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,891,567

Dated June 24, 1975 Inve Charies J. Norton and David 0. Fa] k It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, Iine CoIumn 1, line Column 1, line C01 umn 1, Iine Column 2, line C01 umn 4, Iine CoIumn 4, line [SEAL] deIete "8/18/72" and substitute therefor --7/18/72-- delete "8/17/73" and substitute therefor -7/17/73-- delete "3,886,310" and substitute therefor --3,776,310-- insert the foIIowing cross reference --U.S. Pat. No. 3,779,917 issued 12/18/73,-

deIete "are" and substitute therefor -isdeIete "experiments" and substitute therefor RU C M ASON DONALD W. BANNER Arresting Oflicer Commissioner of Patents and Trademark: 

1. COMPOSITIONS COMPRISING AQUEOUS SOLUTIONS OF ABOUT 0.001% TO ABOUT 10% OF PARTIALLY HYDROLYZED POLYACRYLAMIDE AND ABOUT 0.001% TO ABOUT 10% OF CARBOXY VINYL POLYMERS, THE PERCENTS BASED ON TOTAL WEIGHT OF THE SOLUTION.
 2. Compositions according to claim 1 wherein the partially hydrolyzed polyacrylamide had a molecular weight of about 500,000 to about 20,000,000 and is hydrolyzed to about 0.1 to about 70% of theory.
 3. Compositions according to claim 1 wherein the partially hydrolyzed polymer is present in a concentration of about 0.01 to about 1.0%.
 4. A composition according to claim 1 wherein the aqueous solution is characterized by a viscosity of about 1.5 to about 1, 000 centipoises.
 5. A composition according to claim 1 wherein the aqueous solution is characterized by a viscosity of about 5 to about 500 centipoises.
 6. A composition according to claim 1 wherein the aqueous solution is characterized by a viscosity of about 10 to about 100 centipoises.
 7. Compositions according to claim 1 wherein the carboxy vinyl polymer has a molecular weight above 100,000.
 8. Compositions according to claim 1 wherein the carboxyl vinyl polymer has a molecular weight within the range of about 500,000 to about 20,000,000.
 9. Compositions according to claim 1 wherein the concentration of carboxyl vinyl polymer is about 0.01 to about 1.0%.
 10. Compositions according to claim 1 wherein the partially hydrolyzed polyacrylamide polymer is hydrolyzed about 1 to about 45%. 